Method and system for enhancing accuracy in ultrasonic alignment

ABSTRACT

A method for short range alignment using ultrasonic sensing is provided. The method includes shaping an ultrasonic pulse on a first device to produce a pulse shaped signal and transmitting the pulse shaped signal from the first device to a second device, receiving the pulse shaped signal and determining an arrival time of the pulse shaped, identifying a relative phase of the pulse shaped signal with respect to a previously received pulse shaped signal, identifying a pointing location of the first device from the arrival time and the relative phase, determining positional information of the pointing location of the first device, and reporting an alignment of three or more points in three-dimensional space. Other embodiments are disclosed.

CROSS REFERENCE

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 12/146,445 filed on Jun. 26, 2008, that application aContinuation-In-Part of U.S. patent application Ser. No. 11/562,410filed Nov. 21, 2006 claiming the priority benefit of U.S. ProvisionalPatent Application No. 60/740,358 filed Nov. 29, 2005, the entirecontents of which are hereby incorporated by reference. This applicationalso claims priority benefit to Provisional Patent Application No.61/291,725 filed Dec. 31, 2009, the entire contents of which are herebyincorporated by reference.

FIELD

The present invention generally relates to the field of user interfacenavigation, and more particularly, to pointing devices.

INTRODUCTION

Motion sensing systems detect movement or general location of an object.As one example, a radar unit transmits and receives high energy signalsfor detecting a large metallic object. High energy signals reflect ofthe object due to the properties of the metal. As another example, aweather system tracks storm movement. The system determines the stormdistance by measuring a time difference between when a radar signal wasemitted and when a reflection of the radar signal was received. As yetanother example, a security system detects a presence of an objectentering in close proximity by assessing threshold measurements oftransmitted and received energy signals.

Such systems provide general proximity detection and movement tracking.A need however can arise for determining accurate alignment of objects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a pulse shaping sensing unit for range detection inaccordance with one embodiment;

FIG. 1B is an exemplary configuration of a history buffer and indexingtable in accordance with one embodiment;

FIG. 2A is a hand-held portable ultrasonic device for registeringpositional locations in accordance with one embodiment;

FIG. 2B is a Receiver ultrasonic device for reporting positionallocations of the hand-held portable ultrasonic device in FIG. 3 inaccordance with one embodiment;

FIG. 3A is an exemplary system for reporting pointing location andalignment in accordance with one embodiment;

FIG. 3B is an illustration of extension, varus and valgus deviationswith respect to mechanical axis alignment;

FIG. 4 is a method for short range alignment using ultrasonic sensing inaccordance with one embodiment;

FIG. 5 is an illustration of chirp signals used for short-rangedetection in accordance with one embodiment; and

FIG. 6 depicts an exemplary diagrammatic representation of a machine inthe form of a computer system within which a set of instructions, whenexecuted, may cause the machine to perform any one or more of themethodologies disclosed herein.

DETAILED DESCRIPTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

In one embodiment, a system for short range alignment based onultrasonic sensing is provided. The system comprises i) a hand-heldportable ultrasonic device, and ii) a mountable ultrasonic device. Themountable ultrasonic device registers a pointing location of thehand-held portable electronic device, and determines positionalinformation and short range alignment from three or more pointinglocations of the hand-held portable electronic device. The mountableultrasonic device conveys the pointing location to a remote system thatcan display the pointing location and an orientation of the hand-heldportable ultrasonic device.

The hand-held portable ultrasonic device includes three ultrasonictransmitters for each transmitting a first, second and third pulseshaped ultrasonic signal through the air, an electronic circuit forgenerating driver signals to the three ultrasonic transmitters forgenerating the first, second and third pulse shaped ultrasonic signal,an user interface that receives user input for registering a pointinglocation of the wand device responsive to the user input, acommunications port for relaying the user input and receiving timinginformation to control the electronic circuit, and a battery forpowering the electronic circuit and associated electronics on the firstdevice.

The mountable ultrasonic device includes a processor for generatingtiming information that includes pulse shape parameters, and processingreceived pulse shaped ultrasonic signals, a communications interface fortransmitting the timing information to a hand-held portable ultrasonicdevice that in response shapes and transmits a first, second and thirdpulse shaped ultrasonic signal according to the timing information,three microphones for each receiving the first, second and third pulseshaped ultrasonic signals transmitted through the air, a memory forstoring the first, second and third pulse shaped signals to produce ahistory of received first, second and third pulse shaped signals, and abattery for powering the processor and associated electronics on thesecond device.

FIG. 1A shows a sensing unit 100 for short range detection. The sensingunit 100 can include a pulse shaper 101 for producing a pulse shapedsignal, at least one transmit sensor 102 for transmitting the pulseshaped signal, and at least one receive sensor 102 for receiving thepulse shaped signal. The transmit sensor 102 and receive sensor 102 canbe the same element to provide both transmit and receive operations. Aprocessor 107 operatively coupled to the sensors identifies a locationand orientation of the sensing unit 100 from the pulse shaped signalreceived and reflecting off an object, and a memory 106 for storing ahistory of pulse shaped signals and associated parameters. The receivesensor 102 can be operatively coupled to the pulse shaper 101 and thephase detector 109. The phase detector 109 can identify a phase of thepulse shaped signal, and the processor 107 can use the phase to identifythe location and orientation of the sensing unit 100. The processor 107can include additional processing logic such as thresholds, comparators,logic gates, and clocks for detecting an object's motion.

The sensors 102 can be an array (e.g., line, rows, cols, etc.) or otherarranged pattern (e.g., cross, triangle, circle, etc.) of sensingelements. As one example, the sensing element 102 can be an ultrasonictransmitter and ultrasonic receiver for transmitting and receivingultrasonic signals. In another arrangement, the sensing element 102 canbe an array of microphones and speakers for transmitting and receivingultrasonic and audio signals. As one example, the sensing unit 100 canemploy pulse-echo detection of reflected ultrasonic signals fordetermining its orientation with respect to an object within itsproximity. The sensing unit 100 can be an Application SpecificIntegrated Circuit (ASIC) or Field Programmable Gate Array (FPGA) orother fabricated electronic or analog component. In another arrangement,the sensing element can be CCD camera elements or MEMS camera elementsfor processing light.

FIG. 1B illustrates an exemplary history 110 stored in the memory 106for saving transmitted and/or received pulse shaped signals. The history110 can include an index entry 112, an error entry 114, and a pulseshaped signal waveform entry 116. The error entry can identify errorsfor nearest pulse shaped signal neighbor as well as all pulse shapedsignal waveforms in the history 110 (transmit and receive signals). Theerror entry 404 can be a matrix.

One method of operation by way of the processor 107 stores the latest Npulse shaped signals (transmit and/or receive) in a memory bank; BANK0.As new pulse shaped signals are received for storage into BANK0, everyother (or every 3^(rd) 4^(th) etc.) pulse shaped signals in BANK0 ismoved into another bank; BANK1. Then as pulse shaped signals in BANK1are replaced, the process of moving every other (or every 3^(rd) 4^(th),etc.) pulse shaped signals in BANK1 into another bank, call it BANK2, isrepeated. This process can continue until sufficient pulse shapedreceive signals are stored to realize the T_(max) requirement whilesignificantly reducing the amount of memory required to store thetraces.

In another arrangement the sensing unit 100 can be partitioned out to afirst device and a second device to separate the transmit operation fromthe receive operation. In this configuration, a system for short rangetracking via ultrasonic sensing is provided. FIG. 2A illustrates oneembodiment of a first device 200 with TXs (transmit sensors) 201-203 toprovide transmit operation. FIG. 2B illustrates one embodiment of asecond device 220 with RXs (receive sensors) 221-222 to provide receiveoperation.

The first device 200 shown in FIG. 2A comprises three ultrasonictransmitters 201-203 for each transmitting a first, second and thirdpulse shaped signal through the air, an electronic circuit (orcontroller) 214 for generating driver signals to the three ultrasonictransmitters 201-203 for generating the first, second and third pulseshaped signal, an user interface 218 that receives user input forperforming short range alignment determination, a communications port216 for relaying the user input and receiving timing information tocontrol the electronic circuit 214, and a battery 215 for powering theelectronic circuit 215 and associated electronics on the first device200. The first device 200 102 can include an attachment mechanism 205for coupling to a structure, bone or jig. The first device 200 maycontain more or less than the number of components shown; certaincomponent functionalities may be shared as integrated devices.

Additional ultrasonic sensors can be included to provide anover-determined system for three-dimensional sensing. The ultrasonicsensors can be MEMS microphones, ultrasonic receivers, ultrasonictransmitters or combination thereof. As one example, each ultrasonictransducer can perform separate transmit and receive functions. Oneexample of an ultrasonic sensor is disclosed in U.S. patent applicationSer. No. 11/683,410 entitled “Method and Device for Three-DimensionalSensing” filed Mar. 7, 2007 the entire contents of which are herebyincorporated by reference. The ultrasonic sensor can transmit pulseshaped waveforms in accordance with physical characteristics of acustomized transducer and provided waveform construction shape.

A tip 207 of the first device 200 indirectly identifies points ofinterest on a structure, for example, a rod, bone, instrument or jig inthree-dimensional space. Although the tip is not equipped withultrasonic transducers, its spatial location in three-dimensional spaceis established by the three ultrasonic transmitters 201-203. It can beheld in the hand as a wand to identify via the (wand) tip 207, points ofinterest such as (anatomical) features on the structure, bone or jig.The tip 207 can be touch sensitive to registers points responsive to aphysical action, for example, touching the tip to an anatomical orstructural location. The tip can comprise a mechanical accelerometer oractuated spring assembly. In another arrangement it includes acapacitive touch tip or electrostatic assembly for registering touch.

The user interface 218 can include one or more buttons to permithandheld operation and use (e.g., on/off/reset button) and illuminationelements to provide visual feedback. The first device 200 may furtherinclude a haptic module with the user interface 218. As an example, thehaptic module may change (increase/decrease) vibration to signalimproper or proper operation. The first device 200 provides material tocover the transmitters 201-202 to be transparent to sound (e.g.,ultrasound) and light (e.g., infrared) yet impervious to biologicalmaterial such as water, blood or tissue. In one arrangement, a clearplastic membrane (or mesh) is stretched taught; it may vibrate underresonance with a transmitted frequency. The battery 215 can be chargedvia wireless energy charging (e.g., magnetic induction coils and supercapacitors).

The first device 100 can include a base attachment mechanism 205 forcoupling to a structure, bone or a jig. As one example, the mechanismcan be a magnetic assembly with a fixed insert (e.g., square post head)to permit temporary detachment. As another example, it can be a magneticball and joint socket with latched increments. As yet another example,it can be a screw post to an orthopedic screw.

The first device 200 can further include an amplifier 213 and anaccelerometer 217. The amplifier enhances the signal to noise ratio oftransmitted or received signals. The accelerometer 217 identifies 3 and6 axis tilt during motion and while stationary. The communicationsmodule 216 may include components (e.g., synchronous clocks, radiofrequency ‘RF’ pulses, infrared ‘IR’ pulses, optical/acoustic pulse) forsignaling to the second device 220 (FIG. 2B). The controller 214, caninclude a counter, a clock, or other analog or digital logic forcontrolling transmit and receive synchronization and sequencing of thesensor signals, accelerometer information, and other component data orstatus. The battery 215 powers the respective circuit logic andcomponents.

The controller 214 can utilize computing technologies such as amicroprocessor (μP) and/or digital signal processor (DSP) withassociated storage memory 108 such a Flash, ROM, RAM, SRAM, DRAM orother like technologies for controlling operations of the aforementionedcomponents of the device. The instructions may also reside, completelyor at least partially, within other memory, and/or a processor duringexecution thereof by another processor or computer system. AnInput/Output port permits portable exchange of information or data forexample by way of Universal Serial Bus (USB). The electronic circuitryof the controller can comprise one or more Application SpecificIntegrated Circuit (ASIC) chips or Field Programmable Gate Arrays(FPGAs), for example, specific to a core signal processing algorithm.The controller can be an embedded platform running one or more modulesof an operating system (OS). In one arrangement, the storage memory maystore one or more sets of instructions (e.g., software) embodying anyone or more of the methodologies or functions described herein.

The second device 220 shown in FIG. 2B comprises a processor 233 forgenerating timing information, registering a pointing location of thefirst device 200 responsive to the user input, and determining shortrange alignment from three or more pointing locations of the firstdevice 200 with respect to the second device 220. It includes acommunications interface 235 for transmitting the timing information tothe first device 200 that in response transmits the first, second andthird pulse shaped signals. The pulse shaped signals are a combinationof amplitude modulation, frequency modulation, and phase modulation.Three microphones 221-223 each receive the first, second and third pulseshaped signals transmitted through the air. The memory 238 stores thefirst, second and third pulse shaped signals to produce a history ofpulse shaped signals. The wireless communication interface(Input/Output) 239 wirelessly conveys the positional information and theshort range alignment of the three or more pointing locations to aremote system. The remote system can be a computer, laptop or mobiledevice that displays the positional information and alignmentinformation in real-time as described ahead. The battery powers theprocessor 233 and associated electronics on the second device 220. Thesecond device 200 may contain more or less than the number of componentsshown; certain component functionalities may be shared or thereinintegrated.

Additional ultrasonic sensors can be included to provide anover-determined system for three-dimensional sensing. The ultrasonicsensors can be MEMS microphones, ultrasonic receivers, ultrasonictransmitters or combination thereof. As one example, each ultrasonictransducer can perform separate transmit and receive functions. Oneexample of an ultrasonic sensor is disclosed in U.S. patent applicationSer. No. 11/683,410 entitled “Method and Device for Three-DimensionalSensing” the entire contents of which are hereby incorporated byreference. The second device 220 can include an attachment mechanism 240for coupling to bone or a jig. As one example, the mechanism 240 can bea magnetic assembly with a fixed insert (e.g., square post head) topermit temporary detachment. As another example, it can be a magneticball and joint socket with latched increments.

The second device 220 can further include an amplifier 232, thecommunications module 235, an accelerometer, and processor 233. Theamplifier 232 enhances the signal to noise of transmitted or receivedsignals. The processor 233 can include a controller, counter, a clock,and other analog or digital logic for controlling transmit and receivesynchronization and sequencing of the sensor signals, accelerometerinformation, and other component data or status. The accelerometer 236identifies axial tilt (e.g., 3/6 axis) during motion and whilestationary. The battery 234 powers the respective circuit logic andcomponents.

The communications module 235 can include components (e.g., synchronousclocks, radio frequency ‘RF’ pulses, infrared ‘IR’ pulses,optical/acoustic pulse) for local signaling (to wand 102). It can alsoinclude network and data components (e.g., Bluetooth, ZigBee, Wi-Fi,GPSK, FSK, USB, RS232, IR, etc.) for wireless communications with aremote device (e.g., laptop, computer, etc.). Although externalcommunication via the network and data components is herein contemplate,it should be noted that the second device 220 can include a userinterface 237 to permit standalone operation. As one example, it caninclude 3 LED lights 224 to show three or more Wand tip pointinglocation alignment status. The user interface 237 may also include atouch screen or other interface display with its own GUI for reportingpositional information and alignment.

The processor 233 can utilize computing technologies such as amicroprocessor (μP) and/or digital signal processor (DSP) withassociated storage memory 108 such a Flash, ROM, RAM, SRAM, DRAM orother like technologies for controlling operations of the aforementionedcomponents of the terminal device. The instructions may also reside,completely or at least partially, within other memory, and/or aprocessor during execution thereof by another processor or computersystem. An Input/Output port permits portable exchange of information ordata for example by way of Universal Serial Bus (USB). The electroniccircuitry of the controller can comprise one or more ApplicationSpecific Integrated Circuit (ASIC) chips or Field Programmable GateArrays (FPGAs), for example, specific to a core signal processingalgorithm or control logic. The processor can be an embedded platformrunning one or more modules of an operating system (OS). In onearrangement, the storage memory 238 may store one or more sets ofinstructions (e.g., software) embodying any one or more of themethodologies or functions described herein.

FIG. 3A depicts one exemplary embodiment of a system 300 using the firstdevice 200 and second device 220 suitable for use as a positionalmeasurement and alignment tool for orthopedic applications. The exampleillustrated is a system and method for intra-operatively assessesalignment of the femur and tibia bones.

The system 300 includes the hand-held portable ultrasonic device 301(hereinafter Wand) and the optional mountable ultrasonic device 302(hereinafter Receiver). The Wand 301 and Receiver 302 are low costdisposable components that can be delivered in a sterilized package. TheReceiver 302 can communicate with the remote system 304 to report wandtip location, positional information and an orientation of the wand 301in real-time. The Wand 301 and the Receiver 302 communicate directlywith one another without outside reliance on a supervisory system; thatis, the receiver 302 can determine the location and orientation of theWand 301 within local view and with respect to its own coordinatesystem.

The Wand 301 is used to register points of interest in three-dimensionalspace with respect to the Receiver 302; points of interest can bespatial locations, for example, anatomical or structural locations on abone or structure 312. The Wand 301 can also measure and report distance(e.g., mm, cm) between registered spatial points, for example, a gapdistance between the distal femur and proximal tibia to determine asuitable sized insert. It can also be used to identify displacement, forexample, an edge point or perimeter trace of an insert relative to itsprojected insertion location. The Wand 301 can also thereafter beaffixed at these locations to report rotations and translations of theunderlying object (e.g., bone, jig, insert, prosthetic etc) at thesepoints, for example, relative to a reference orientation. This alsopermits for full range tracking and reporting of kinematic behavior.Such information can be used during the surgery to report range of jointmotion and for comparison of post-surgical results.

In one embodiment, the system 300 comprises the Receiver 302 coupled tothe jig 312, and the Wand 301 to register points of interest on a firstand second bone with respect to the jig 312. The Receiver 302 and Wand301 employ ultrasonic sensing and tracking to determine the Wandsorientation and location relative to the Receiver 302 and the jig 312.Based on the registered points of interest, the Receiver 302 assessesand reports parameters related to the orientation of the jig 312 foraligning the first and second bone. The wand tip locations andorientations can also be stored for reference on the Receiver 302.Similarly, the system 300 can report alignment of the bones or jigs 312by way of the Wand 301 and the Receiver 302 from these points ofinterest. The system 300 can assist in assessing alignment of the jigs312 and bones for example, in knee replacement procedures. Softwareconfigurable parameters permit operation beyond the 3 m applicationrange shown.

In one example, alignment is achieved when the points of the femur head(A′), knee center (B′) and ankle (C′) are positioned in a straight lineas indicated by a positioning location of the Wand tip 301 at the secondlocations at separate times. Femur head identification of point (A′) canbe determined by affixing the Receiver 302 to the distal end of thefemur and placing the Wand 301 at a stationary location in view (e.g., 1m distance from Receiver 302). The femur is then rotated in a patternfor approximately 10-15 seconds to resolve the spherical center (femurhead) as described in Provisional Patent Application No. 61/291,725while the hip is sufficiently still. Upon establishing point (A′), thewand tip is then used to register the knee center (e.g., distal femurcenter) point B′ when the leg is in flexion. Other anatomical locationscan be registered fro providing further alignment information, forexample, the proximal tibia. Thereafter, the wand tip is used toregister the medial malleolus and the lateral malleolus whichestablishes the ankle center C′ (e.g., eq:center=0.6*medial<x,y,z>)+0.4*lateral<x,y,z>).

Once these three (or more) points A′, B′ and C′ are registered, the Wand301 can be affixed midway on the tibia and in view of the Receiver 302.This permits real-time tracking of the tibia relative to the femur bonewhen the leg is in extension (straight) or in flexion (bent). In thisfixed relationship, the Receive 302 can track a position and orientationof the Wand 301 relative to the Receiver's own coordinate system whichinherently reveals any rotations and translations of the tibia relativeto the femur (e.g., axial twist, left-right, up-down, forward-backward,and combinations thereof). As noted previously, this permits the system300 to track and report a range of motion and associated kinematicinformation (e.g., axial twist, rotations, alignment) in accordance witha patient's expected orthopedic behavior during the procedure.

Certain aspects of alignment preparation can be performed before hand;for example, calibrating the Receiver 302 to the jig 312 or Wand 301. Itcan also transmit the positional information to associated wirelessdevices (e.g., laptop, cell phone, net book) like the remote system 304and upload the information to a server on a network for example oneconnected to electronic medical or health care records. The system 300can assess and report in real-time the position of these points fordetermining alignment, or other registered points, by way of a graphicaluser interface on the communication device 304.

FIG. 3B shows alignment along a mechanical axis of a leg for normal andabnormal conditions. In extension, the femur 321 and tibia 322 of theleg are aligned along the mechanical axis (MA). The MA is approximatelyθ˜=6 degrees 325 from the vertical (V) at the ankle; and approximately15-18 degrees from the vertical (V) at the knee (Q-angle) for a straightleg in standing position. As illustrated in the center subplot, a varusdeformity is an outward angulation of the distal segment of a bone orjoint with an alignment angle (or error) described by −Φ327. Asillustrated in the right subplot a valgus deformity is a term for theinward angulation of the distal segment of a bone or joint with analignment angle (or error) described by +Φ327.

The system 300 reports the alignment angle Φ327 between the first line341 and the second line 342 as part of the positional location(information). The first line 341 is defined by the pointing location ofthe Wand 301 at a first point A′ at a first time and a second point B′at a second time. The second line 342 is defined by the pointinglocation of the Wand 301 at the second point B′ and a third point C′ ata third time. The pointing locations as determined by the pulse shapedsignals are stored in the history for reference. The system 300 caninclude multiple points for determining alignment and is not limited toa 3-point profile.

As previously indicated the Receiver 302 itself can display alignmentinformation or report the information to remote system to providevisualization. As one example, the LED lights 224 on the Receiver 302illuminate in accordance with a detected alignment. A single multi-colorLED will turn green for perfect alignment (0°), turn yellow if less than2°, and turn red if alignment is off by 3° or more. With single colorLEDS, a varus condition will illuminate the corresponding medial(inside) LED, a valgus condition will illuminate the correspondinglateral (outside) LED, and an alignment less than 1° will show all LEDSgreen. Other illumination patterns are herein contemplated and are notlimited to those described. Similarly, the GUI 307 can report alignmentinformation via text representation of the alignment error or by colorcoding displayed line segments.

FIG. 4 depicts an exemplary method 400 for short range alignment usingultrasonic sensing by way of the alignment system shown in FIG. 3A. Themethod 400 can be practiced with more or less than the number of stepsshown and is not limited to the order shown. To describe the method 400,reference will be made to FIGS. 2A, 2B, 3A and 5, although it isunderstood that the method 400 can be implemented in any other suitabledevice or system using other suitable components. Moreover, the method400 is not limited to the order in which the steps are listed in themethod 400 In addition, the method 400 can contain a greater or a fewernumber of steps than those shown in FIG. 4

The method can begin at step 402 in which the Wand 301 shapes anultrasonic pulse signal to produce a pulse shaped signal and at someseparation distance transmits the pulse shaped signal to the Receiver302. The transmitter 201 receives from the controller 214 a driversignal that describes the pulse shape to be transmitted. As one examplethe shape can be a square wave that causes a transducer of thetransmitter 201 to resonate. In another arrangement, the driver signalcan be a frequency modulated or amplitude modulated driver signalprovided by the controller 214. One example of pulse shaping is taughtin U.S. Pat. No. 7,414,705 entitled “Method and System for RangeMeasurement” the entire contents of which are hereby incorporated byreference.

The pulse shape can be previously stored in a local memory of thecontroller or external memory 208 that is referenced prior totransmission. Alternatively, timing information provided to thecontroller 214 from the Receiver 302 can include pulse shape informationor pulse shape parameters in real-time; that is, the Receiver 302directs the Wand 301 to transmit ultrasonic pulse signals with aspecified shape and at a specified time. The shaping comprisesgenerating an amplitude modulated region, frequency modulated region,constant frequency region, phase modulated region, a chirp region, or acombination thereof as described ahead in FIG. 5.

The Receiver 302 by way of the processor 233 at step 404 receives thepulse shaped signal and determines an arrival time of the received pulseshaped signal. One example of detecting arrival time is taught in U.S.patent application Ser. No. 11/562,404 entitled “Method and System forObject Control” the entire contents of which are hereby incorporated byreference. This can further include calculating a first Time of Flightof a first pulse shaped signal emitted at a first time from a firsttransmitter on the first device and received on a first microphone onthe second device, calculating a second Time of Flight of a first pulseshaped signal emitted at a second time from a second transmitter on thefirst device and received on a second microphone on the second device,and calculating a third Time of Flight of a first pulse shaped signalemitted at a third time from a third transmitter on the first device andreceived on a third microphone on the second device. That is, a time offlight is calculated for each microphone based on the transmitting ofonly one pulse shaped waveform.

In a first arrangement, the Receiver 302 is wired via a tetheredelectrical connection (e.g., wire) to the Wand 301. That is, thecommunications port of the Wand 301 is physically wired to thecommunications interface of the Receiver 302 for receiving timinginformation. The timing information from the Receiver 302 tells the Wand301 when to transmit and includes optional parameters that can beapplied to the ultrasonic signal for pulse shaping. The processor on theReceiver 302 employs this timing information to establish the first,second and third Time of Flight measurements with respect to a referencetime base.

In a second arrangement, the Receiver 302 is communicatively coupled tothe Wand 301 via a wireless signaling connection. As previouslyindicated an infrared transmitter on the Wand 301 can transmit aninfrared timing signal with each transmitted pulse shaped signal. TheReceiver 302 can include a photo diode for determining when the infraredtiming signal is received. In this case the communications port of Wand301 is wirelessly coupled to the communications interface of theReceiver 302 by way of the infrared transmitter and the photo diode forrelaying the timing information to within 3 microsecond accuracy (˜1 mmresolution). The processor on the Receiver 302 employs this infraredtiming information to establish the first, second and third Time ofFlight measurements with respect to a reference transmit time.

At step 406, the Receiver 302 by way of the processor 233 identifies arelative phase of the pulse shaped signal with respect to a previouslyreceived pulse shaped signal. One example of detecting relative phase istaught in U.S. patent application Ser. No. 11/146,445 the entirecontents of which are hereby incorporated by reference. This can furtherinclude calculating a first phase differential between the first pulseshaped signal and a previously received pulse shaped signal bothcaptured at the first microphone, calculating a second phasedifferential between the first pulse shaped signal and a previouslyreceived pulse shaped signal both captured at the second microphone; andcalculating a third phase differential between the first pulse shapedsignal and a previously received pulse shaped signal both captured atthe third microphone. That is a differential time of flight iscalculated for each microphone based on the transmitting of a firstpulse shaped waveform and a previously received pulse shaped waveformeach at the respective microphone stored in the history.

The Receiver 302 by way of the processor 233 at step 408, identifies apointing location of the Wand 301 tip 207 with respect to a coordinatesystem of the Receive 302 from the arrival time of the received pulseshaped signal and the relative phase. The processor 233 converts thetime of flight and differential time of flight measurements calculatedfrom each of the received pulse shaped signals at the three microphonesto three spatial points, and transforms the three spatial points to X, Yand Z rotations at the positional location to determine an orientationof the first device. A positional location is where the wand tip 207 islocated in three-dimensional space with respect to an orientation of theWand 301. The positional location can be represented in Cartesian<x,y,z> coordinates or r*sin/cos polar coordinates. It can be the samepoint in three-dimensional space even though the wand orientation (e.g.,tilt, rotation).

Continuing with method 400, as shown in step 410, most recent pulseshaped signals are saved to a history, and at step 412 pulse shapedsignals less recently saved in the history are selectively discarded.The selective pruning of pulse shaped signals in the history is based ona similarity measure between previous pulse shaped signals for furtherand more efficiently resolving the pointing location. This approachsaves most recent n (index 403 into history) or n small, since there aretypically many echo waveform changes in the near time. In contrast, theechoes from far-time (past time) can be selectively pruned based oncurrent distance measures (e.g., L2 norm, spectral distortion,log-likelihood, MSE, energy metrics). In practice, the most recent nechoes can be saved, and echoes from longer ago in the history can beselectively discarded based on the distances, to create a sparse historythat is weighted more heavily in the near-time than in the far-time.

The step of selectively discarding pulse shaped signals includesselectively pruning the history based on one among an L2 norm based,spectral distortion based, log-likelihood based, or mean-squared errorbased metric, creating a sparse history of pulse shaped signals based ona difference rate between pulse shaped signals, and updating an indextable to the pulse shaped signals in the history according to the sparsehistory, wherein the sparse history weights echoes more heavily in thenear-time than in the far-time. This step can further includeiteratively scanning through the history to identify an index 112 forthe pulse shaped signals where an distortion difference (e.g. error 114)is significantly greater than a noise difference.

At step 414, the Receiver 302 determines positional information of thepointing location of the Wand 301 at three or more points inthree-dimensional space. The Wand 301 and the Receiver 302 each havetheir own local coordinate system. The Receiver 302 maps the wandcoordinate system to its own local coordinate system by a series oftranslations and rotations given the transmitter locations on the Wand301 and the microphone locations on the Receiver 302. One example ofmapping coordinates via ultrasonic sensing is taught in U.S. patentapplication Ser. No. 11/566,148 entitled “Method and System for MappingVirtual Coordinates” the entire contents of which are herebyincorporated by reference.

The Receiver 302 determines time of flight and relative phase of thereceived pulse shaped signals at each of the microphones, and calculatesthe spatial locations of the Wand 301 transmitters with respect to theReceivers 302 local coordinate system (at the origin). The Receiver 302thereafter applies a series of translations and rotations to map theWand's 301 local coordinate system to the Receiver's 302 localcoordinate system. This transformation establishes an orientation of theWand 301 and positional location of the wand tip relative to theReceiver 302. The mapping includes i) the Wand 301 dimensions (e.g.,10×3×10 cm <w,l,h>) and component layout for the local coordinates ofthe transmitters and the wand tip that are predetermined, and ii) theReceiver 302 dimensions (e.g., 6×2×8 cm, <w,l,h>) and component layoutfor the local coordinates of the microphones and its coordinate originthat are predetermined.

The Receive 302 at step 416 reports the positional information and analignment of the three or more points. The positional informationidentifies the Wand 301 tip location relative to the Receiver 302 andoptionally the spatial coordinates of the three or more Wand 301transmitters relative to the coordinate system of the Receiver 302. Itcan be reported via sensory feedback, graphical or text display and/oraudibly. One example of sensory feedback via ultrasonic sensing and itsprinciples of operation is taught in U.S. patent application Ser. No.11/562,413 entitled “Method and System for Sensory Feedback” the entirecontents of which are hereby incorporated by reference. As shown in FIG.3A, the positional information and the alignment can be rendered to a 3Drepresentation; for example, alignment of the femur and tibia. The GUI307 displays real-time updates to permit the user to visualize andassess multiple-point alignment. In the example shown, alignment isreported for varus and valgus deviations in accordance with the wand tippositional locations.

The method 400 repeat operation of the method steps 402 to 416 tocontinually update the positional location of the Wand 301 tip and theWand's orientation. That is, the Receiver 302 continually tracks theWand 301 location as it is moved in three-dimensional space. It canupdate the GUI 307 in response to a user directive when the user pressesthe wand button to register a point. The Wand 301 can also beindependently mounted to another object to report position andorientation of that object. This permits the system 300 to trackrelative movement or position of one object (e.g., femur) with respectto another object (e.g., tibia).

In another embodiment, a method for short range alignment usingultrasonic sensing is provided. The method includes shaping threeultrasonic pulse signals on a first device to generate three pulseshaped signals and transmitting the three pulse shaped signals by way ofthree transmitters on the first device to a second device, receiving thethree pulse shaped signals at each of three microphones on the seconddevice and determining three arrival times for the three pulse shapedsignals received at the three microphones, identifying three relativephases of the three pulse shaped signals with respect to previouslyreceived pulse shaped signals at the three corresponding microphones onthe second device, identifying a pointing location of a tip of the firstdevice with respect to a coordinate system of the second device from thethree arrival times of the received pulse shaped signals and the threerelative phases of the received pulse shaped signals, determiningalignment of three or more registered pointing locations of the firstdevice at three or more three-dimensional locations and at separatetimes by repeated operation of the method steps above, and reporting analignment of the three or more pointing locations.

Transmit times for each of the three pulse shaped signals can be delayedby transmitting a first ultrasonic pulse signal at a first time,transmitting a second ultrasonic pulse signal at a second time, andtransmitting a third ultrasonic pulse signal at a third time. A portionof each pulse shaped signal can include a frequency modulated region,constant frequency region, phase modulated region, or a chirp region.This permits estimating the pointing location from a frequency modulatedregion for each of the three received pulse shaped signal, and anorientation from the relative phase from a continuous frequency regionfor each of the three received pulse shaped signals.

The method steps can be repeated to further include saving most recentpulse shaped signals to a history, and selectively discarding pulseshaped signals less recently saved in the history based on a similaritymeasure between pulse shaped signals in the history for furtherresolving the pointing location. In a wireless arrangement timinginformation is transmitted from the first device to the second device toindicate a pulse shape and when to transmit each pulse shaped signal.

Referring to FIG. 5, a pair of chirp signals 510 and 520 is shown.Briefly, the chirp signals are sent from the Wand 301 in a direction ofthe Receiver 302 and captured at the Receiver 302. It should also benoted that in certain embodiments both devices can transmit and receivechirp signals. The chirp signals are condition pulse signals thatimprove a detection of the pulse.

The pulse shaper can be implemented as a combination of software andhardware on the controller 214 in the Wand 301 (see first device 200).It can produce a linear chirp 510 or a quadratic chirp 520. The pulseshaper by way of the controller 214 can produce numerous types of chirpsignals, of which 512 and 522 are provided for illustration. It shouldalso be noted that the second device 220 (Receive 302) can generatepulse shape information that is instead transmitted to the Wand 301which in response generates the pulse shaped signals. In this case, theWand 301 receives directives from the Receiver 302 to adjust the shapingand/or timing sequence of transmitted pulse shaped signals.

In one example, the linear chirp 512 can be represented as a frequencymodulated sine wave with linearly increasing frequency 514. As anotherexample, the linear chirp 512 can also be represented as a piece-wiselinear function shown in 516. For instance, the first portion of thechirp signal 516 can contain constant frequency modulation followed by asecond portion which can be a linearly increasing frequency modulation.The chirp signal is not limited to being linearly modulated. Forexample, the pulse shaper 101 can produce a quadratic chirp signal 520.The quadratic chirp signal 520 can be characterized by a non-linearlyvarying frequency modulation with a quadratic phase. The chirp signal522 can be represented by the frequency and time characteristics of plot524. As can be seen, the frequency increases in an exponential fashionwith time. The exponential frequency increase can be seen in theincreased periodicity of the time signal 522.

From the foregoing descriptions, it would be evident to an artisan withordinary skill in the art that the aforementioned embodiments can bemodified, reduced, or enhanced without departing from the scope andspirit of the claims described below. For example, the system 300 can bedeployed in industrial settings for assessing alignment, medical fieldfor assessing a positional relationship among objects, or mechanicaldevices or drills for aligned guidance. From the embodiments of FIGS.1-6 it should be evident to one of ordinary skill in the art that thereare innumerable ways to use the sensor system. Accordingly, the readeris directed to the claims for a fuller understanding of the breadth andscope of the present disclosure.

FIG. 6 depicts an exemplary diagrammatic representation of a machine forsupporting operation of the sensor device in the form of a computersystem 600 within which a set of instructions, when executed, may causethe machine to perform any one or more of the methodologies discussedabove. In some embodiments, the machine operates as a standalone device.In some embodiments, the machine may be connected (e.g., using anetwork) to other machines. In a networked deployment, the machine mayoperate in the capacity of a server or a client user machine inserver-client user network environment, or as a peer machine in apeer-to-peer (or distributed) network environment.

The machine may comprise a server computer, a client user computer, apersonal computer (PC), a tablet PC, a laptop computer, a desktopcomputer, a control system, a network router, switch or bridge, or anymachine capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. It will beunderstood that a device of the present disclosure includes broadly anyelectronic device that provides voice, video or data communication.Further, while a single machine is illustrated, the term “machine” shallalso be taken to include any collection of machines that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

The computer system 600 may include a processor 602 (e.g., a centralprocessing unit (CPU), a graphics processing unit (GPU, or both), a mainmemory 604 and a static memory 606, which communicate with each othervia a bus 608. The computer system 600 may further include a videodisplay unit 610 (e.g., a liquid crystal display (LCD), a flat panel, asolid state display, or a cathode ray tube (CRT)). The computer system600 may include an input device 612 (e.g., a keyboard), a cursor controldevice 614 (e.g., a mouse), a mass storage medium 616, a signalgeneration device 618 (e.g., a speaker or remote control) and a networkinterface device 620.

The mass storage medium 616 may include a computer-readable storagemedium 622 on which is stored one or more sets of instructions (e.g.,software 624) embodying any one or more of the methodologies orfunctions described herein, including those methods illustrated above.The computer-readable storage medium 622 can be an electromechanicalmedium such as a common disk drive, or a mass storage medium with nomoving parts such as Flash or like non-volatile memories. Theinstructions 624 may also reside, completely or at least partially,within the main memory 604, the static memory 606, and/or within theprocessor 602 during execution thereof by the computer system 600. Themain memory 604 and the processor 602 also may constitutecomputer-readable storage media.

Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays andother hardware devices can likewise be constructed to implement themethods described herein. Applications that may include the apparatusand systems of various embodiments broadly include a variety ofelectronic and computer systems. Some embodiments implement functions intwo or more specific interconnected hardware modules or devices withrelated control and data signals communicated between and through themodules, or as portions of an application-specific integrated circuit.Thus, the example system is applicable to software, firmware, andhardware implementations.

In accordance with various embodiments of the present disclosure, themethods described herein are intended for operation as software programsrunning on a computer processor. Furthermore, software implementationscan include, but not limited to, distributed processing orcomponent/object distributed processing, parallel processing, or virtualmachine processing can also be constructed to implement the methodsdescribed herein.

The present disclosure contemplates a machine readable medium containinginstructions 624, or that which receives and executes instructions 624from a propagated signal so that a device connected to a networkenvironment 626 can send or receive voice, video or data, and tocommunicate over the network 626 using the instructions 624. Theinstructions 624 may further be transmitted or received over a network626 via the network interface device 620.

While the computer-readable storage medium 622 is shown in an exampleembodiment to be a single medium, the term “computer-readable storagemedium” should be taken to include a single medium or multiple media(e.g., a centralized or distributed database, and/or associated cachesand servers) that store the one or more sets of instructions. The term“computer-readable storage medium” shall also be taken to include anymedium that is capable of storing, encoding or carrying a set ofinstructions for execution by the machine and that cause the machine toperform any one or more of the methodologies of the present disclosure.

The term “computer-readable storage medium” shall accordingly be takento include, but not be limited to: solid-state memories such as a memorycard or other package that houses one or more read-only (non-volatile)memories, random access memories, or other re-writable (volatile)memories; magneto-optical or optical medium such as a disk or tape; andcarrier wave signals such as a signal embodying computer instructions ina transmission medium; and/or a digital file attachment to e-mail orother self-contained information archive or set of archives isconsidered a distribution medium equivalent to a tangible storagemedium. Accordingly, the disclosure is considered to include any one ormore of a computer-readable storage medium or a distribution medium, aslisted herein and including art-recognized equivalents and successormedia, in which the software implementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the disclosure is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP, USB) representexamples of the state of the art. Such standards are periodicallysuperseded by faster or more efficient equivalents having essentiallythe same functions. Accordingly, replacement standards and protocolshaving the same functions are considered equivalents.

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of apparatus and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Otherembodiments may be utilized and derived therefrom, such that structuraland logical substitutions and changes may be made without departing fromthe scope of this disclosure. Figures are also merely representationaland may not be drawn to scale. Certain proportions thereof may beexaggerated, while others may be minimized. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

Other examples of positional measurement and alignment for orthopedicapplications are herein contemplated. As another example a system andmethod for positioning and inserting a hip cup is provided. The Wand tipcan register three locations on the hip to identify a docking target fora hip cup. The Wand 301 can then be affixed to a cup insert instrumentto track its orientation relative to the registered docking target. Athird example is a system and method for visualizing and reportingvertebral alignment in spine applications. The wand tip can registermultiple location on the sacrum to identify a base coordinate system.The wand can then be affixed (or touched) to a vertebra to reportalignment relative to the sacrum. The Wand can also be used to trace andreport a spine contour for before and after comparison.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

1. A method for short range alignment using ultrasonic sensing,comprising: shaping an ultrasonic pulse signal on a first device toproduce a pulse shaped signal and transmitting the pulse shaped signalfrom the first device to a second device; receiving the pulse shapedsignal and determining an arrival time of the pulse shaped signalreceived at the second device; identifying a relative phase of the pulseshaped signal with respect to a previously received pulse shaped signalat the second device; identifying a pointing location of a tip of thefirst device with respect to the second device from the arrival time ofthe received pulse shaped signal and the relative phase; saving mostrecent pulse shaped signals to a history; selectively discarding pulseshaped signals less recently saved in the history based on a similaritymeasure between pulse shaped signals in the history for furtherresolving the pointing location; determining positional information ofthe pointing location of the first device at three or more points inthree-dimensional space; and reporting the positional information and analignment of the three or more points, wherein the shaping uses acombination of amplitude modulation, frequency modulation, and phasemodulation.
 2. The method of claim 1, comprising estimating the pointinglocation from a frequency modulated region for the received pulse shapedsignal, and an orientation from the relative phase from a continuousfrequency region for the received pulse shaped signal.
 3. The method ofclaim 1, comprising calculating a first Time of Flight of a first pulseshaped signal emitted at a first time from a first transmitter on thefirst device and received on a first microphone on the second device;calculating a second Time of Flight of a first pulse shaped signalemitted at a second time from a second transmitter on the first deviceand received on a second microphone on the second device; andcalculating a third Time of Flight of a first pulse shaped signalemitted at a third time from a third transmitter on the first device andreceived on a third microphone on the second device.
 4. The method ofclaim 2, comprising calculating a first phase differential between thefirst pulse shaped signal and a previously received pulse shaped signalboth captured at the first microphone; calculating a second phasedifferential between the first pulse shaped signal and a previouslyreceived pulse shaped signal both captured at the second microphone; andcalculating a third phase differential between the first pulse shapedsignal and a previously received pulse shaped signal both captured atthe third microphone; and determining the pointing location of the firstdevice from first, second, and third Time of Flight and the first,second and third phase differential.
 5. The method of claim 1, furthercomprising converting the time of flight and differential time of flightmeasurements calculated from each of the received pulse shaped signalsat the three microphones to three spatial points; transforming the threespatial points to X, Y and Z rotations around the first device at thepositional location to determine an orientation of the first device. 6.The method of claim 1, where reporting the alignment identifies an anglebetween a first line and a second line, where the first line is definedby a first point at a first time and a second point at a second time,and the second line is defined by the pointing location of the firstdevice at the second point and a third point at a third time.
 7. Themethod of claim 1, wherein short range detection between the firstdevice and the second device is 5 cm to 2 m with an angle of the firstdevice and the second device at 60 degrees or less.
 8. The method ofclaim 1, wherein the step of selectively discarding pulse shaped signalscomprises: selectively pruning the history based on one among an L2 normbased, spectral distortion based, log-likelihood based, or mean-squarederror based metric; creating a sparse history of pulse shaped signalsbased on a difference rate between pulse shaped signals; and updating anindex table to the pulse shaped signals in the history according to thesparse history, wherein the sparse history weights echoes more heavilyin the near-time than in the far-time.
 9. A method for short rangealignment using ultrasonic sensing, the method steps comprising: shapingthree ultrasonic pulse signals on a first device to generate three pulseshaped signals and transmitting the three pulse shaped signals by way ofthree transmitters on the first device to a second device; receiving thethree pulse shaped signals at each of three microphones on the seconddevice and determining three arrival times for the three pulse shapedsignals received at the three microphones; identifying three relativephases of the three pulse shaped signals with respect to previouslyreceived pulse shaped signals at the three corresponding microphones onthe second device; identifying a pointing location of a tip of the firstdevice with respect to a coordinate system of the second device from thethree arrival times of the received pulse shaped signals and the threerelative phases of the received pulse shaped signals; determiningalignment of three or more registered pointing locations of the firstdevice at three or more three-dimensional locations and at separatetimes by repeated operation of the method steps above; and reporting analignment of the three or more pointing locations, wherein at least oneportion of each pulse shaped signal is at least one among a frequencymodulated region, constant frequency region, phase modulated region, anda chirp region.
 10. The method of claim 9, wherein the step ofidentifying the pointing location comprises: estimating the pointinglocation from a frequency modulated region for each of the threereceived pulse shaped signal, and an orientation from the relative phasefrom a continuous frequency region for each of the three received pulseshaped signals.
 11. The method of claim 9, comprising delaying atransmit time for each of the three pulse shaped signals by:transmitting a first ultrasonic pulse signal at a first time;transmitting a second ultrasonic pulse signal at a second time; andtransmitting a third ultrasonic pulse signal at a third time.
 12. Themethod of claim 11, comprising: wirelessly transmitting timinginformation from the first device to the second device to indicate apulse shape and when to transmit each pulse shaped signal.
 13. Themethod of claim 9, comprising repeating the method steps to include:saving most recent pulse shaped signals to a history; and selectivelydiscarding pulse shaped signals less recently saved in the history basedon a similarity measure between pulse shaped signals in the history forfurther resolving the pointing location.